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The FBI announced a nationwide manhunt, as agents are looking for a Bay Area man who is considered armed and dangerous. The manhunt was issued after agents, in full hazmat gear, said they found explosive materials in his apartment on Russian hill. NBC Bay Area’s Jodi Hernandez reports from the scene. (Published Sunday, Jun 1, 2014)

Updated at 8:28 AM EDT on Monday, Jun 2, 2014

The FBI has launched a nationwide manhunt for a man named Ryan Kelly Chamberlain II in connection with Sunday's investigation at an apartment building in San Francisco's Russian Hill neighborhood.

FBI agents, San Francisco police and fire crews, and a hazardous materials team swarmed the building between Jackson and Polk streets early Saturday morning in a search that continued into the early hours of Sunday.

FBI Swarm SF Building, Seek Man For Explosive Material

A nationwide manhunt is underway Sunday after FBI agents and hazmat crews raided a San Francisco apartment--and came away with potentially explosive chemicals. Police are looking for 42-year-old Ryan Chamberlain, and they warn the public he is considered armed and dangerous. NBC Bay Area's Jodi Hernandez reports from San Francisco with more. (Published Sunday, Jun 1, 2014)

FBI spokesperson Peter Lee said at a press conference Sunday that the FBI is looking for Chamberlain, 42, a San Francisco resident, for possession of explosive material at his residence.

“If you have any sort of sightings or if you know him, please just let us know, so we can help apprehend him, and again, bring him in so people are safe,” Lee said.

FBI, Hazmat Crews Outside Russian Hill Apt. Building

NBC Bay Area has learned that agents are removing a chemical from a San Francisco apartment building that is deadly if not handled correctly. Some agents are using hazmat gear in the raid that is still going on Saturday night in the Russian Hill neighborhood. NBC Bay Area’s Kimberly Tere reports with the more on this developing story. (Published Sunday, Jun 1, 2014)

Chamberlain is 6' 3" tall, weighs 225 lbs and has blue eyes and brown hair, according to Lee. He was last seen south of San Francisco Sunday, driving a white 2008 Nissan Altima with a California or Texas license plates of either 7FQY085 or BX9M042. He is believed to be wearing a dark blue hooded sweatshirt and blue jeans and is considered armed and dangerous, Lee said.

The FBI is encouraging anyone with any information on Chamberlain to notify the agency at 415-553-7400 or call 911.

FBI, Hazmat Crews Outside SF Building

Dozens of emergency crews swarmed an apartment building on Russian Hill in San Francisco Saturday--many of them are in full hazmat gear. NBC Bay Area’s Kimberly Tere has more on the investigation. (Published Saturday, May 31, 2014)

The San Francisco FBI office told NBC Bay Area Sunday that the agency was executing a search warrant at Chamberlain's apartment as part of a criminal investigation.

"HiddenCash" Frenzy in San Jose

the FBI said the investigation poses "no threat to public safety," and that protective equipment had been used Sunday in the interest of agent safety. Lee said that contrary to what was reported by some news sources, there was no conclusive evidence of the deadly poison ricin at Chamberlain's apartment.

An FBI spokesperson said that a bomb squad had shown up at the scene of the investigation, but that it turned out to be a false radiation alarm.

An FBI source told NBC Bay Area that crews found a chemical in the apartment that, if not handled correctly, can kill. The person may have bought the chemical -- which is often used in assisted suicide situations -- on the internet, according to the source.

The FBI declined further comment on the intent or motive behind the explosive material in light of the ongoing investigation.

Crews wearing hazmat suits were seen going in and out of the building and people gathered on the roof of the building, according to a witness. More than a dozen bags of evidence were collected Saturday.

"Actually, as I was walking down here, I thought it was a film set," onlooker Faisal Choudry said. "And somebody said the FBI is here investigating, and they’ve been here since the morning."

Police blocked off a section of Jackson Street between Polk Street and Van Ness Avenue Saturday. Jackson street was reopened around 12:30 a.m. and fire and hazmat crews left the scene Sunday morning.

Those who live in the area said it had been an interesting afternoon.

"There are a lot of police, a lot of fire, and there was a bomb squad here earlier," neighbor Dianne Dubois said. "That's very scary for those of us who live here, but it seems like everything is going OK. But it's hard to know. We don't know anything about what's going on, so we have no information at all."

Neighbors said that the FBI had not told them anything about the investigation.

Those who live inside the building told NBC Bay Area the FBI has taken at least two computers from the apartment.

Neighbors said they do not know much about the man who lives in the unit except he is in his 40s and works in marketing. They described him as quiet and polite.

"I know this person who lives in this apartment," Fechtar said. "It’s just kind of weird. He seems like a nice guy, and he probably is."

NBC Bay Area has learned Chamberlain worked as a social media consultant and also has experience in political campaigns, according to his social media web sites.

The past chair of the San Francisco Republican Party, Howard Epstein, has confirmed Chamberlain served on the Republican Central Committee in San Francisco before switching over to the Democratic Party.

Epstein said he was absolutely stunned.

“To have the explosives and all that is just totally mind-boggling to me,” Epstein said. “Well, I’m hoping that he turns himself in. I hope he doesn’t get into any more trouble. I don’t know what he’s thinking. I don’t know what he’s been doing the last few years, what’s going on in his head. I’m just hoping that this all comes out and nobody gets hurt.”

When reporters asked Lee whether the FBI is using Chamberlain's apparent social media presence to help with the investigation, Lee declined comment or confirmation that the online accounts belonged to Chamberlain.

Chamberlain's warrant and affidavit are currently sealed, Lee said. His apartment is being treated as an active crime scene and currently remains sealed, he said.